1. Field of the Invention
The present invention is directed to agents for causing the enhancement of seed yield when applied to leguminous plants.
2. Description of Related Art
Diflubenzuron {N-(2,6-difluorobenzoyl)-N'-(4-chlorophenyl)urea} is an insect growth regulator that is active on many foliar feeding insects of soybeans, cotton, etc. It has previously been determined that the use of diflubenzuron can increase soybean seed yields, even when pest infestations are lower than the economically damaging threshold. This increase has been demonstrated when diflubenzuron was applied between the full bloom and beginning seed reproductive stages. It was unclear, however, as to how diflubenzuron could be increasing seed yield, since it binds readily to plant surfaces, is not considered to be translocated throughout the plant, and rarely is ever detected in the seed.
Diflubenzuron, which is commercially available as Dimilin.RTM. (Uniroyal Chemical Company, Inc.) belongs to the substituted 1-benzoyl-3-phenylurea family of pesticides and acts by interfering with the production/deposition of chitin, one of the main components of the insect exoskeleton.
After treatment with diflubenzuron, larvae have difficulties with the molting process, which results in an inability to cast off the old exoskeleton successfully and leads to the eventual death of the larvae. The mode of action of the diflubenzuron also gives rise to trans-ovarial effects by interfering with chitin deposition of the developing larva in the egg. Diflubenzuron exhibits long residual on plant tissue, but readily dissipates in soil or aqueous media. The compound is not considered systemic in the plant and therefore sucking insects are not usually affected.
Diflubenzuron provides control of a number of important pests in a variety of fruits, field crops, pasture and turf, horticulture and fish waters. Dimilin is labeled to control soybean pests that include velvetbean caterpillar (Anticarsia gemmatalis), Mexican bean beetle (Epilachna varivestis), green cloverworm (Plathypena scabra), beet armyworm (Spodoptera exigua), and fall armyworm (Spodoptera frugiperda). These insects can be considered economically damaging pests in soybeans grown in the southern United States; green cloverworm can occasionally cause significant damage in the northern United States.
The application of diflubenzuron to soybeans for controlling such pests can be made up to 21 days from harvest. A total of 0.062 lb a.i./acre/year (about 70 gm a.i./ha/year) can be applied. Typically, soybeans are treated for control of foliar feeding insects during the plant's reproductive period up to the point where damage will no longer limit final seed yield. The reproductive period can be segmented into different stages. Fehr et al. (Stages of Soybean Development, Special Report 80, 11 pages, Cooperative Extension Service, Iowa State University, Ames (1981)) describe eight "R" stages. They are RI, or beginning bloom; R2, or full bloom; R3, or beginning pod; R4, or full pod; R5, or beginning seed; R6, or full seed; R7, or beginning maturity; and R8, or full maturity.
These growth stages apply to both the determinate soybeans typically grown in the southern United States, and the indeterminate soybeans typically grown in the northern United States, except that R1 and R2 generally occur simultaneously in determinate varieties. Fehr et al also describe other differences in plant development between indeterminate and determinate varieties.
Up to 80% of the flowers formed on a soybean plant can be aborted as a flower or a pod (see van Schaik et al., Agron. J 50:192-197 (1958)) regardless of whether the plant is determinate or indeterminate. Additionally, van Schaik et al., supra, cite papers that describe other legumes (e.g., peanut, lima beans, white pea beans) and cotton as having a high number of flowers and/or fruit structures aborted.
U.S. Pat. No. 3,450,747 discloses that the compound N-(3,4-dichlorobenzoyl)-N'-(3,4-dichlorophenyl)urea has a herbicidal and/or insecticidal activity.
U.S. Pat. No. 3,748,356 discloses 2,6-dihalobenzoyl ureas that are said to be useful as insecticides. More specifically, the compounds are of the formula: ##STR2##
where
A is a hydrogen atom, a halogen atom, a methyl group or a methoxy group, PA1 B also represents a hydrogen atom, a halogen atom, a methyl group or a methoxy group, with the proviso that A and B do not both represent a hydrogen atom, PA1 X and Y each represent an oxygen atom or a sulfur atom, PA1 R is a hydrogen atom, an alkyl group, a hydroxy group, an alkoxy group, an alkoxymethyl group, an acyl group or an alkoxycarbonyl group, PA1 R.sub.1 is a hydrogen atom, an alkyl group which may be substituted with halogen, with alkoxy, with alkylthio or with cyano, a 1-cycloalkenyl group, a benzyl group which may be substituted with halogen, a hydroxy group, an alkoxy group, an acyl group, an alkoxycarbonyl group, an alkoxythiocarbonyl group, an alkylsulfonyl group or a phenylsulfonyl group, while furthermore R and R.sub.1 together with the group ##STR3## PA1 indicated in the above formula may form a ring system, and PA1 R.sub.2 represents a substituted or non-substituted phenyl group or a pyridyl group which may be substituted with halogen, with nitrocyano or with halogenated alkyl. PA1 (a) 1-3 halogen atoms, PA1 (b) 1-2 alkyl groups, possibly substituted with halogen, hydroxy, alkoxy, alkylthio, dialkyl amino, alkylsulphonyl and phenyl, PA1 (c) Tri- or tetramethylene, PA1 (d) A cycloalkyl group, possibly substituted with halogen or cyano, PA1 (e) 1-2 nitro groups or cyano groups or alkoxy groups, PA1 (f) A dioxymethylene or dioxy ethylene group, PA1 (g) An acyl group, which may be substituted with halogen, PA1 (h) An alkyl sulfonyl, phenyl sulfonyl, alkylthio, phenylthio or phenoxy group, which groups may be substituted with halogen, PA1 (i) A sulfonamide group, which may be alkylated, and PA1 (k) A phenyl group, which may be substituted with halogen, nitro, cyano and halogenated alkyl. PA1 R.sub.10, R.sub.11, R.sub.12, R.sub.13, and R.sub.14 are independently selected from the group consisting of hydrogen, halogen, alkyl, alkenyl, alkoxy, aryl, aryloxy, nitro, cyano, alkylthio, alkylsulfinyl, alkylsulfonyl, and alkylenedioxy. PA1 R.sub.10, R.sub.11, R.sub.12, R.sub.13, and R.sub.14 are independently selected from the group consisting of hydrogen, halogen, alkyl, alkenyl, alkoxy, aryl, aryloxy, nitro, cyano, alkylthio, alkylsulfinyl, alkylsulfonyl, and alkylenedioxy. It is preferred that at least one of R.sub.10, R.sub.11, R.sub.12, R.sub.13, and R.sub.14 be other than hydrogen. PA1 A and B are independently selected from the group consisting of hydrogen, halogen, methyl, and methoxy, X represents an oxygen atom or a sulfur atom, and R.sub.10, R.sub.11, R.sub.12, R.sub.13, and R.sub.14 are as described above. Preferably, A and B are independently selected from the group consisting of chlorine, fluorine, and methyl and, more preferably, X is oxygen.
If R.sub.2 is a substituted phenyl group, the phenyl group contains at least one substituent chosen from the group consisting of:
U.S. Pat. No. 6,057,370 is directed to a method of controlling insects of Lepidoptera on a genetically altered cotton plant having incorporated therein a gene derived from Bacillus thuringiensis (Bt) which codes for and expresses a protein having pesticide activity comprising the steps of applying to the foliage of said genetically altered cotton plant a pesticidally active amount of certain substituted benzoyl urea compounds, e.g., N-(2,6-difluorobenzoyl)-N'-(4-chlorophenyl)urea.
The disclosures of the foregoing are incorporated herein by reference in their entirety.